Prosthetic Structure and A Method For Producing Prosthetic Structure

ABSTRACT

A prosthetic structure and a method to build the same on at least two mounted implants (or implant analogues). A tubular member is releasably mounted on the respective implant. A body, having a throughput channel, is mounted on the respective tubular member to be displaceable along the same. A bar is inserted between two nearby tubular members, and the distances between the respective nearby pairs of ball-and-socket-like shaped and co-operating surfaces of the bodies and of the bar are eliminated. The bar may be of adjustable length, in order to be fitted shape-wise bondingly between two bodies. Alternatively, one of the bodies may be rotatable on the tubular member thereof. The fitted structure is fixed, for instance, by welding, soldering or agglutination of occurring joints.

The invention relates to a method for producing a rigid supportingprosthetic structure of the kind that is seen in the preamble of claim1.

The invention also relates to a device for the production of aprosthetic structure of such kind, according to the preamble of theappended independent device claim.

A requirement for a prosthetic structure to correctly rest againstfixtures, for instance implants, is that no significant stresses shouldoccur in the structure when the same is connected to the fixtures. Suchstresses can establish forces, which tend to displace the fixturesmutually, whereby the patient may experience them as negative. Suchstresses may also lead to an incomplete alignment between co-operatingsupport surfaces on the prosthetic structure and the respectivefixture/implant, so that a tightened mounting screw can get a tendencyof becoming threaded out when the structure is subjected to varyingloads.

The fixtures usually comprise implants, for instance a dental implant.Usually, a model of the jaw of the patient is manufactured using implantanalogues. On the same, a tubular member is releasably mounted by meansof a fixing screw, which extends through the member and having a headthat rests against a seating in the member. The threaded end of thefixing screw engages by a thread in the implant/the implant analogue inorder to bring the support surfaces of the member and the implantanalogue, for instance ring-shaped support surfaces, stably into solidcontact with each other around the fixing member. Between adjacent pairsof such members along a line of implants, for instance dental implantsin one of the jaws of a patient, bars are now to be bridgingly mountedon the members releasably carried by the implant analogues, withoutintroducing any stresses. After that, the formed mounted structure is tobe fixed in the substantially stressless state thereof. The intention isthat the structure then may be provided with a superstructure of aconventional kind per se, for instance corresponding to a dentalprosthesis and/or teeth, in order to, without problems, i.e., withoutintroduction of stresses, subsequently be allowed to be connected to theimplants in the patient by means of said members and the appurtenantfixing screws.

A previously known technique (“DynaStar”) includes that the implantshave cup-shaped upper surfaces and that the bars are telescopic and haveball-shaped end bodies, which are articulately received in the recessesof the implants. The ball-shaped end portions of the bars have athroughput opening each for a fixing member, which with the threadedportion thereof is received in a central threaded boring in the implantand which by means of the head thereof clamps the ball down in therecess of the implant. In the mounting operation, the telescopic bar maybe given a chosen length, and furthermore, the telescopic bar partsshould be mutually fixed by welding, for the formation of a rigid andstiff structure that may be dismounted from the implants/the implantanalogues.

A problem of the previously known structure is, however, that the ballsof the bars should rest on the cup-shaped upper ends of the implants,whereby the possibility of displacement of the connection point of thebar along the axis of the implant cannot be attained in a simple way.

Another drawback is that the structure relies on telescopic bars, whichmeans difficulties when the distances between adjacent implants aresmall.

An object of the invention is, therefore, to provide a method and a newdevice by means of which said drawbacks may be obviated entirely orpartly.

The object is attained by the invention.

The invention is defined in the appended independent claims.

Embodiments of the invention are defined in the appended dependentclaims.

Important features of the invention is that a body having a throughputchannel is mounted on and displaced along a tubular member, which isreleasably mounted on an implant/implant analogue at a desired axialposition along said member. The body defines the position of theconnection points of the connecting bars. This position may, in otherwords, be set by a chosen displacement of the body along the tubularmember. The tubular member and the body should co-operate by a certainfriction, for instance with a threaded joint or a frictional fitting,allowing the body to be displaced along the member by means of manuallypressed forces into a chosen position.

When the distances between adjacent implants/implant analogues arerelatively great, it may be advantageous to utilize axiallyextensible/shortenable (“telescopic”) bars, the end portions of whichare, for instance, cup-shaped, concave and co-operate with the (forinstance, convex) surface portions of the bodies adapted thereto, inorder to adjust the same bars to the correct length and into shapewisebonding to the bodies. But when the distances between the implants/theimplant analogues are relatively short, instead it may be advantageousto utilize bars having fixed length. Thus, a bar may be selected from aset or series of bars of different length. One of the two bodies towhich the bar is to be joined, may have an oval shape.

In relation to the previously known structure, which also requires thatthe screw head and the ball have articulately co-operating surfaceshaving a centre of curvature that substantially coincides with thecentre of curvature of the co-operating fusion faces of the ball and theimplant, the invention also offers the advantage of allowing a greaterrange of deflection between the implant axis and the axis of theconnecting bar.

In the structure according to the invention, at least one of the ballsmay have a protruding arm that forms a corbelling-out part of thestructure, for instance for the extension of a dental prostheticstructure.

In the following, the invention will be described by way of examples,reference being made to the appended drawing.

FIG. 1 schematically shows a side view of a prosthesis as mounted onimplants or implant analogues.

FIG. 2 shows a view taken along the line II-II in FIG. 1.

FIG. 3 schematically illustrates an implant having a tubular membermounted thereon and a body mounted thereon.

FIGS. 4 and 5 show in axial section two different embodiments of a bar,which may be used in the invention.

FIG. 6 schematically illustrates a fixed bar, as joined between twoadjacent bodies, one of which is oval.

FIG. 7 schematically illustrates an alternative embodiment of theco-operating surface sectors of the body and of the bar.

FIG. 8 shows a view taken along the line VIII-VIII in FIG. 7.

FIG. 9 shows a variant of the object of FIG. 7.

FIG. 10 shows a view taken along the line X-X in FIG. 9.

FIGS. 1 and 2 illustrate a prosthetic structure carried by threeimplants. Each implant 10 carries a tubular member 20 that rests againstthe implant 10 and is releasably connected to the same by a fixingmember 21, which by means of a thread engages in a threaded boring 11 inthe implant 10. The member 20 has a step 22 that forms a seating for thehead 23 of the fixing member 21. The tubular member 20 has asubstantially constant outer cross section along the length thereof. Aball 30 has a throughput opening 31 and is threaded on the member 20.The wall of the opening 31 may, for instance, be in the form of athread, which threadably engages with a corresponding outer thread (notshown) on the outside (circumference surface) of the member 20, so thatthe ball 30 may be displaced axially along the member 20 and assume asubstantially stable axial position along the same. As an alternative tothe thread, the wall 31 of the throughput opening and/or thecircumferential surface of the member 20 may have scores or a surfaceroughness offering a limited frictional coupling between the ball andthe member, whereby an operator may displace the ball 30 manually alongthe member 20 into a chosen position, where the ball stays. As anadditional alternative, the ball and the member may have a mutual fitthat offers a similar frictional binding.

The throughput channel of the ball is shown to have widened sections 32at the ends in order to facilitate for the operator to thread the ball30 onto the member 20.

The implant 10 is shown to have a thread 12, by means of which theimplant is anchored in bone tissue 13, for instance in the jawbone of apatient when the implant 10 is to support a dental prosthesis.

FIGS. 1 and 2 illustrate three structures corresponding to FIG. 3, a bar40 being shown inserted between adjacent pairs of bodies 30, which areshown in the form of balls. The bar 40 has opposite end portions 37,which are cup-shaped by a radius substantially corresponding to theradius of the balls 30. As can be seen in FIGS. 1 and 2, the bars 40 areshown to be axially adjustable in respect of the length, in order to, ina relatively short state, be possible to be inserted between twoadjacent balls 30, and there be expanded until the cup-shaped endsurfaces thereof come into surface-extended contact with the balls onthe sides thereof facing each other.

As shown in FIG. 4, the bar 40 may comprise two parts 42, 43 thatmutually are axially directed for linear motion, for instance by thefact that one part 43 has a protruding pin 44, which is received in acorresponding guiding channel 45 in the other part 42. Preferably, theparts 44, 45 may engage by a certain limited friction against each otherso that the bar 40 may be adjusted manually into chosen the length andkeep this length, as inserted between a pair of balls 30. As anotheralternative, a spring, for instance a compression spring 47, may bereceived in the channel 45 between the bottom thereof and the pin 44,for prestressing the bar 40 toward the maximal length thereof,preferably defined by co-operating stop faces on the two parts. In thisway, an operator may compress the bar 40 before the same is insertedbetween two adjacent balls 30, and subsequently the bar is released andallowed to expand, under the effect of the spring 47, into contact withthe respective ball.

FIG. 5 shows an axial section through another embodiment of a bar 40,comprising two parts 42, 43, one of which has a bar 44 that is receivedin a boring 45 in the other part 42. In FIG. 5, the bar 44 and thechannel 45 are shown to have co-operating screw threads 51, 52.Alternatively, the threads 51, 52 may be replaced by scores or surfaceirregularities allowing the parts 42, 43 to be mutually axiallydisplaced and to keep the adjusted length up to a certain axial load.

It will be appreciated that the structure 60 shown in FIG. 1 after thebuilding up thereof and after the fitting of the included members toeach other, substantially has no stresses that tend to deform thestructure, in particular the members 20 away from their set positions onthe implants 10. Furthermore, it will be appreciated that the buildingup of the structure may include that the balls 30 are displaced alongthe members 20 into chosen axial positions along the members 20, i.e.,to chosen distances from the implants 10. Next, the fitted structureaccording to FIGS. 1 and 2 may be fixed by the fact that the bars 40 arefixed in the adjusted length and by the fact that the bars 40 arefixed/joined to the balls 30 and the balls 30 are fixed to the members20. The fixation may be provided by means of glue joints, welded joints,soldered joints. In the case of welded joints, the parts may first bejointed to each other by welding by means of welding spots and then thesame are supplemented with welding seams.

In a particularly preferred embodiment, the cup-edge may be chamfered inthe respective end of the bar 40, such as shown at 48 in FIG. 3, inorder to define, with the surface 36 of the ball 30, a circumferentialV-shaped gap 49, which facilitates establishment of a welding seam orglue joint between the bar and the ball. The chamfering in the ends ofthe throughput channel 31 of the ball also allows facilitatedaccessibility to the joint between the channel wall 31 of the ball andthe outer circumference of the member, for the assurance of, forinstance, a welding seam.

In a few embodiments, axially adjustable bars 40 may bridge over a greatdistance range between adjacent balls 30, but when the distance betweenadjacent balls 30 becomes small, in certain cases it is preferred toform the bars 40 to have constant length. In order to, in a such case,be able to insert such bars 40′ between two balls in a simple way, oneof the balls 30 may have an elliptical shape, i.e., have a varyingradius around the circumference thereof in relation to the axis of thethroughput channel 31, so that the ball has at least one substantiallyspherical bulge 38 of advanced radius R. When the bulge 36 extendssubstantially perpendicularly from the connecting line between twoadjacent balls 30, a bar 40′ of fixed length may be inserted between theballs in order to then be fitted shape-wise bondingly in between thesame by turning the oval ball 30′ into alignment to the axis of the bar40′. Alternatively, the body may be entirely round, but have athroughput opening that is eccentrically located in relation to theenvelope surface of the body.

FIG. 1, finally, shows a ball 30 that is mounted at one end of theprosthesis, and may have a cantilever arm 39, which is intended toprovide an extension of the prosthesis arc that is built up past thelast implant 10 in the row.

A person skilled in the art appreciates that the structure 60 does notnecessarily need to be built up on the implant 10 in the jaw of apatient, but may be built up on an implant analogue in a model of thejaw of the patient. When the structure 60 has been fixed, a prosthesismay be built up on the same, wherein the prosthesis, for instance, maycomprise tooth members and prosthesis parts, when the construction is adental prosthesis. It will be appreciated, however, that the prosthesisshows general use, even if it primarily has been developed in order toprovide dental bridge constructions and the like, which should bereleasably fixed to the implant 10.

Thanks to the invention, the structure 60 may easily be given a shapethat does not have any built-in stresses and that, therefore, does nothave any tendency to deviate from the shape it has been given in thebuilding up on the implants/the implant analogues.

FIGS. 8-10 illustrate that the bodies 30, as an alternative to a convexball cap area for the co-operation with a concave end surface of thebar, may have a rounded recess that receives a corresponding roundedconvex end part of the bar, for the formation of a ball-and-socket-likejoint between the body and the bar.

In the embodiment according to FIG. 6, where the bar has a fixed lengthand a concave end surface for the co-operation with a convexly rounded,preferably spherical surface sector of the body 30, and because thissurface sector has a centre of curvature that coincides with the axis ofrotation of the body (and the end surface of the bar has a correspondingcurvature), the fitting of the bar to the body may be effected by thefact that the body is rotated while the bar is kept aligned to the axisof rotation of the body.

Suitably, the bodies have two substantially diametrically opposedsurface sectors for the co-operation with a respective bar end.

In other cases (FIGS. 8-10), it is, in the fitting of bars having fixedlength, suitable to ensure that the bar turns around the opposite endthereof that rests against an adjacent body at the same time as thefreely movable end thereof-follows the surface sector in question of thebody during the turning motion of the body for the shape-wise bondingengagement. In this way, a shape-wise bonding between the body and thebar end is offered, also when the central portion of the bar has a fixedlength corresponding to the free distance that can be adjusted betweentwo bodies.

The concave surface portion of the bar end, for instance, is suitablycup-shaped and lacks undercut, the cup-shape receiving the convexsurface portion of a radially protruding part of the body in such a waythat it is possible to change the direction of the bar end in relationto the body. For instance, the concave surface has a greater radius thanthe convex one. When the first bar end is received on a first body, theco-operating surface portions of the second body and of the other end ofthe bar should be able to move into engagement with each other duringturning, about in the same way as a cog and a gash of two co-operatingcogwheels.

As can be seen in FIG. 3, the bar end may have a concave surface 37,which co-operates with the generally spherical outer surface of a body30 formed as a ball. Alternatively, the radially protruding portion 38of the body may have a curved surface that offers a surface-extendedcontact with the cup-shaped surface 37 of the bar end. Naturally, thebody 30 may have, for instance, two generally diametrically opposedprotruding portions 38.

1. Method for producing a prosthetic structure on a patient modelcontaining implant analogues, a bar being connected to two adjacentimplant analogues and being fixed to the same, wherein a sleeve isreleasably mounted on the end of the respective implant analogue inaxial alignment to the same, that each sleeve is provided with a bodydisplaceable in longitudinal direction of the sleeve and having athrough guiding channel that receives the sleeve, that each body isdisplaced along the respective sleeve into a selectable axial position,that co-operating pairs of the surface portion of the body and the barend are substantially complementary, one of the surface portions beingconcavely cup-shaped, and that the bar is mounted in substantially axialalignment between adjacent bodies, the distance between the bar ends andthe bodies being eliminated for the shape-wise bonding of the barbetween the pair of adjacent bodies, whereupon the prosthetic structureformed by the sleeves, the balls and the bars is fixed by welding,soldering or agglutination.
 2. Method according to claim 1, wherein thebar is axially variable in length and is axially inserted between a pairof bodies and is extended so that the bar ends shape-wise bondinglyco-operate with nearby surface portions of the adjacent bodies and thatthe fixation of the structure includes a fixation of the bar in theadjusted length thereof.
 3. Method according to claim 1, wherein thedistance between the ends of the bar and the bodies is eliminated by thefact that the bar has a preselected length, and that at least one of thebodies is rotatable around the tubular member thereof and has saidsurface portion thereof located at another radial distance from the axisof rotation of the body than adjacent surface parts of the body, andthat the bar is bonded shape-wise between the pair of bodies by turningof the rotatable body.
 4. Method according to claim 3, wherein one endof the bar, which preferably is cup-shapedly concave, articulately restsagainst a convex surface portion of an adjacent body, the co-operablesurface portions of the other body and of the other end of the bar beingkept near each other, the bar being turned into axial alignment betweenthe bodies at the same time as the other body being rotated in order toallow mutual shape-wise bonding.
 5. Method according to claim 3, whereina set of bars of graded lengths is provided and that a bar is selectedfrom the set to have a central axial length corresponding to the minimumdistance between the pair of bodies when the bar is aligned between thebodies.
 6. Method according to claim 2, wherein the bar comprises twomutually axially displaceable parts, which by means of friction orthreaded joint may be adjusted manually into a chosen length that iskept after manual unloading.
 7. Method according to claim 2, wherein thetwo parts of the bar are mutually axially guided and that a spring isarranged to prestress rod parts mutually toward an axially chosenmaximum value of the length of the bar.
 8. Method according to claim 1,wherein the throughput channel of the body and the outside of the sleevehave co-operating formations that allow manual axial mutual adjustmentof the position of the body along the tubular member and that in theabsence of external load retains the body in the set axial position. 9.Method according to claim 1, wherein the sleeve has an inner seating fora screw head of a screw, which releasably engages by a thread in theimplant.
 10. Device for the building up of a prosthetic structure, whichbridges over two implants in a patient or bridges over two implantanalogues in a model of the patient, comprising a bar, which extendsbetween and is connected to the implants, wherein a sleeve is releasablymounted on one end of the implant/the implant analogue in axialalignment to the same, that each sleeve carries a body, which has athroughput channel, in which the sleeve is received, that the body isarranged displaceably into a chosen position along the sleeve, and thatco-operating pairs of surface portions of the body and the bar aresubstantially complementary, one of the surface portions being concavelycup-shaped, and that means are provided for the shape-wise bonding ofthe ends of the bar to the respective nearby bodies.
 11. Deviceaccording to claim 10, wherein the means comprises that the bar islinearly adjust-able in length.
 12. Device according to claim 10,wherein the means comprises that at least one of the bodies that connectto the ends of a bar has a surface portion having a greater radialdistance to the axis of rotation of the ball around the tubular memberthan nearby surface in the direction of rotation, and that the bar has afixed length.
 13. Device according to claim 10, wherein the throughputchannel of the body widens towards at least one of the ends of thethroughput channel.
 14. Device according to claim 10, wherein the edgeof the concave surface portion is chamfered.
 15. Device according toclaim 10, wherein the ball co-operates with the tubular member by meansof a threaded joint or a friction joint that offers simple materialdisplacement of the body along the tubular member, but in the absence ofexternal load retains the body in the set displaced position.
 16. Deviceaccording to claim 10, wherein the parts of the device, after mutualfitting to each other, are intended to be fixed by being fixedlyconnected to each other for the formation of a prosthetic structure. 17.Device according to claim 10, wherein the body preferably is in the formof a ball and that the bar ends are concave.
 18. Method according toclaim 4 wherein a set of bars of graded lengths is provided and that abar is selected from the set to have a central axial lengthcorresponding to the minimum distance between the pair of bodies whenthe bar is aligned between the bodies.
 19. Device according to claim 12,wherein the means comprises that at least one of the bodies that connectto the ends of a bar has a surface portion having a greater radialdistance to the axis of rotation of the ball around the tubular memberthan nearby surface in the direction of rotation, and that the bar has afixed length.
 20. Device according to claim 15, wherein the parts of thedevice, after mutual fitting to each other, are intended to be fixed bybeing fixedly connected to each other for the formation of a prostheticstructure.